Breeding goals can be simple or complex. In case of commercial breeding programs many traits are recorded and have an influence on the profit of animals produced by these commercial breeding programs. In extensive production conditions or in case of hobby breeding only a few important traits are recorded and simple breeding goals consisting of a few traits are used.
In order to rank the individual selection candidates for the breeding goal traits it is necessary to comprise the values for the respective traits into one single selection criterion. The value of this criterion can be obtained by summing up the breeding value for each trait multiplied by a weighing factor based on the relevance of that trait in the breeding goal. The relevance might be based on the relative economic value of the trait. This principle is outlined in the slide below:
Definition
The Breeding value is the mean genetic value of an individual as a parent for a trait. It is estimated as twice the average superiority of the individual’s progeny relative to all other progeny under conditions of random mating
The economic value of an animal is based on many traits having different effects: production, quality (composition) of the product, disease problems, fertility, and ease of handling and management.
Procedures exist to define breeding goals to weigh market and non-market values. In these procedures animals are seen as an integrated part of a production system (at farm level?). Weighing of traits has been mainly dependent on economic values and frequencies of expression of the genetic gain obtained. The methodology to weigh the traits with respect to resource efficiency and economy is well developed.
A illustrative example of the calculation of the net value of an increase by one unit in a breeding goal trait is given in the slide below:
The composition of traits affects the structure of a breeding program. The breeding goal traits determine from which animals traits should be measured: from parents of the selection candidates, the candidates themselves, their sibs or their progeny? When sib or progeny records are required, they should be bred in sufficient numbers to obtain accurate information for the breeding value of the candidate.
Progeny of selected animals produce at various moments. Therefore it is necessary to relate future income into the present costs of selection.